Abstract: For the reduction of noise signals, and particularly crosstalk signals, in measurement systems for analyzing emission or transmission processes and composed of a serial arrangement of a signal source (1), a measurement path (2) with or without a transmission test object (8), a detector (3), and a measurement and display circuit (5), an identification modulation is imparted to the signal component carried in the measurement path by means of repeated modulation (6, 9). The evaluation of the detector output signal may be performed with respect to a frequency which is free of the effects of the single modulation signals occurring in the detector output signal because of noise pick-up. Use of this method in homodyne systems for quadrupole parameter measurements further eliminates the effects of crosstalk reflections which typically occur in these systems.